=IF(LEFT(CELL("format",A3),1)="D",A3,DATE(LEFT(A3, 4),MID(A3,5,2),RIGHT(A3,2)))

Just a thought might be to ignore the Year and Day.

=IF(LEFT(CELL("format",A3),1)="D",A3,DATE(2000,MID (A3,5,2),1))

= = =
Dana DeLouis


Gary''s Student wrote:
If you must use your formula, then:

=CHOOSE(MONTH(IF(LEFT(CELL("format",A3),1)="D",A3, DATE(LEFT(A3,4),MID(A3,5,2),RIGHT(A3,2)))),"jan"," feb","mar","apr","may","jul","aug","sep","oct","no v","dec")


but easier is:

=IF(LEFT(CELL("format",A3),1)="D",A3,DATE(LEFT(A3, 4),MID(A3,5,2),RIGHT(A3,2)))

and format the cell with the formula as Custom "mmmm"